How to fix my car's alternator that's making a whining sound

I am currently charging my battery using an external charger.

BHPian veek recently shared this with other enthusiasts.

So I reverse the polarity of the alternator battery and a faint smoke was released. When I set it correctly the alternator makes a slight whining sound (no other electricals in the vehicle)

Right now I just get the display and the battery multi-meter shows 11V or so (old battery, should read 12.25V).

Anyhow, I am charging the battery right now with an external charger and wondering what to do? Any help on cost, availability of spares?

I live in Bangalore. (Can I fix this? Don't have any mechanical tools - multi-meter, a few screwdrivers, spanners) Don't use the car much as well; Once in 2-3 months, but parents want it.

Here's what BHPian R2D2 had to say on the matter:

What part did the smoke come from? If you reversed the polarity (a very BIG no-no!) you may have blown an electrical component, maybe the rectifier/regulator. Just pray the ECU is okay.

Ok since you're a tech experienced person in bridge rectifiers I think the best way to check for faults is to:

• Switch on the ignition and check any warning lights come on
• Attempt to start the car - if the ECU is blown it will not start.
• If the car starts take a DMM and measure the voltage at the battery terminals. It should be about 13.5-14.4 volts when the engine is idling.

Mind you if the car needs to be repaired it will have to be taken on a flatbed or a tow truck. You may be looking at a pretty large expense.

Here's what BHPian Indian2003 had to say on the matter:

First, you should give more details about your car. I would think the diodes in the alternator are fried for sure. If the car is old, that should be the least of your problems.

With later models cars, you are looking at some serious cash to fix the car.

Don't try to fix the car yourself. You risk doing more damage.

Does your car have an ECU? What happens when you switch on the ignition? Does the battery lamp light up? Do any of the lamps light up? Does the car start?

Assuming this is an old car without electronics and an alternator, your diodes might be fried. Then you will need to fit a new diode bridge and rectifier or get a new exchange alternator.

It looks like your alternator is not charging at all. If it did you would have measured at least 13,5V at the battery. You should be shopping around for an alternator.

You might have gotten away if you just shorted the wire by mistake but it looks like you connected the cables to the battery. You are also looking at a new battery.

A fully charged battery is at 12,7V and a dead battery at 11,7V. The difference between lif and death is only 1V. At 11V, your battery has taken its last breath.

Here's what BHPian nik0502 had to say on the matter:

Hi veek,

Please start by looking for blown fuses. Something similar happened with my Gypsy a couple of years back and all it took was one fuse to get the car started. If it does not fuse then you might be looking at the alternator and other parts.

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